This study will examine the role of catecholamines, catecholamine metabolism, and vasoactive neuropeptides in the cardiovascular adaptation to exercise training in the elderly. This study will test the hypothesis that inactivation of norepinephrine, epinephrine, and dopamine by sulfation is increased and that plasma levels of vasodilatory neuropeptides, substance P and vasoactive intestinal polypeptide, are increased in the elderly with exercise training.